U.S. patent number 11,179,507 [Application Number 16/845,284] was granted by the patent office on 2021-11-23 for blood purification apparatus.
This patent grant is currently assigned to Nikkiso Company Limited. The grantee listed for this patent is Nikkiso Company Limited. Invention is credited to Kunihiko Akita, Shinya Hasegawa, Satoru Kawarabayashi, Tomoya Murakami, Masahiro Toyoda.
United States Patent |
11,179,507 |
Kawarabayashi , et
al. |
November 23, 2021 |
Blood purification apparatus
Abstract
A blood purification apparatus to which a blood circuit that
allows a patient's blood to extracorporeally circulate and a blood
purifier connected to the blood circuit and that purifies the blood
in extracorporeal circulation are attachable, the blood
purification apparatus including a dialysate introduction line
through which dialysate is introduced into the blood purifier; a
dialysate drain line through which waste dialysate resulting from
blood purification performed by the blood purifier is drained from
the blood purifier; and a concentration-detecting unit that detects
a concentration of a predetermined substance in the waste dialysate
resulting from the blood purification by the blood purifier and
flowing through the dialysate drain line. The blood purification
apparatus includes a control unit that establishes a state of
equilibrium where the concentration of the predetermined substance
in the waste dialysate flowing through the dialysate drain line and
a concentration of the predetermined substance in the blood flowing
through the blood circuit are equal or approximate to each other; a
storage unit storing a value detected by the
concentration-detecting unit in the state of equilibrium as an
equilibrium value; and a clearance-calculating unit that calculates
clearance in accordance with the value detected by the
concentration-detecting unit and the equilibrium value stored in
the storage unit, the clearance being a figure of merit
representing a degree of solute removal by the blood purifier.
Inventors: |
Kawarabayashi; Satoru (Tokyo,
JP), Hasegawa; Shinya (Shizuoka, JP),
Murakami; Tomoya (Shizuoka, JP), Akita; Kunihiko
(Shizuoka, JP), Toyoda; Masahiro (Shizuoka,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Nikkiso Company Limited |
Tokyo |
N/A |
JP |
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Assignee: |
Nikkiso Company Limited (Tokyo,
JP)
|
Family
ID: |
1000005953005 |
Appl.
No.: |
16/845,284 |
Filed: |
April 10, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200237991 A1 |
Jul 30, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2018/038712 |
Oct 17, 2018 |
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Foreign Application Priority Data
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Oct 17, 2017 [JP] |
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2017-201429 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M
1/1609 (20140204); A61M 1/3612 (20140204); A61M
1/3653 (20130101); A61M 2205/3306 (20130101); A61M
2205/3334 (20130101) |
Current International
Class: |
A61M
1/16 (20060101); A61M 1/36 (20060101) |
Field of
Search: |
;604/5.04 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3042672 |
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Jul 2016 |
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EP |
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H03-173569 |
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Jul 1991 |
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JP |
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2016214367 |
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Dec 2016 |
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JP |
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2016/016039 |
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Feb 2016 |
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WO |
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Other References
Extended European Search Report for Application No. 18868950.0,
dated Jun. 22, 2021. cited by applicant.
|
Primary Examiner: Mensh; Andrew J
Attorney, Agent or Firm: Young Basile Hanlon &
MacFarlane, P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION(S)
This application is a continuation of International Application No.
PCT/JP2018/038712, filed on Oct. 17, 2018, which claims priority to
Japanese Application No. 2017-201429, filed on Oct. 17, 2017, the
entire disclosures of which are hereby incorporated by reference.
Claims
The invention claimed is:
1. A blood purification apparatus to which a blood circuit, that
allows a patient's blood to extracorporeally circulate, and a blood
purifier connected to the blood circuit, that purifies the blood in
extracorporeal circulation, are attachable; the blood purification
apparatus including: a dialysate introduction line, through which
dialysate is introduced into the blood purifier; a dialysate drain
line through which waste dialysate resulting from blood
purification performed by the blood purifier is drained from the
blood purifier; and a concentration-detecting unit that detects a
concentration of a predetermined substance in the waste dialysate
resulting from the blood purification by the blood purifier and
flowing through the dialysate drain line; the the blood
purification apparatus further comprising: a control unit that
establishes a state of equilibrium where the concentration of the
predetermined substance in the waste dialysate flowing through the
dialysate drain line and a concentration of the predetermined
substance in the blood flowing through the blood circuit are equal
or approximate to each other; a storage unit storing a value
detected by the concentration-detecting unit in the state of
equilibrium as an equilibrium value; and a clearance-calculating
unit that calculates clearance in accordance with the value
detected by the concentration-detecting unit and the equilibrium
value stored in the storage unit, the clearance being a figure of
merit representing a degree of solute removal by the blood
purifier.
2. The blood purification apparatus according to claim 1, wherein
the clearance-calculating unit calculates clearance through a
mathematical expression CL=(Cd/Cdeq).times.Qd (where CL denotes
clearance, Cd denotes the concentration of the predetermined
substance detected by the concentration-detecting unit, Cdeq
denotes the equilibrium value stored in the storage unit, and Qd
denotes dialysate flow rate).
3. The blood purification apparatus according to claim 1, wherein
the control unit establishes the state of equilibrium by reducing
or stopping a dialysate flow rate, increasing, a blood flow rate,
or causing the dialysate to circulate through the blood
purifier.
4. The blood purification apparatus according to claim 1, wherein
the concentration-detecting unit includes a light-emitting portion
that emits light toward the waste dialysate, a light-receiving
portion that receives the light emitted from the light-emitting
portion and transmitted through the waste dialysate, and a
detecting portion that detects absorbance in accordance with an
intensity of the light received by the light-receiving portion, the
concentration-detecting unit detecting the concentration of the
predetermined substance in the waste dialysate in accordance with
the absorbance detected by the detecting portion.
5. The blood purification apparatus according to claim 4, wherein
the storage unit stores, as the equilibrium value, the absorbance
detected by the detecting portion in the state of equilibrium, and
the clearance-calculating unit calculates clearance in accordance
with the absorbance detected by the detecting portion and the
equilibrium value stored in the storage unit.
6. The blood purification apparatus according to claim 5, wherein
the clearance-calculating unit calculates clearance through a
mathematical expression CL=(Abs/Abseq).times.Qd (where CL denotes
clearance, Abs denotes the absorbance detected by the detecting
portion, Abseq denotes the equilibrium value stored in the storage
unit, and Qd denotes dialysate flow rate).
7. The blood purification apparatus according to claim 1, further
comprising a time-lapse-change-calculating unit that calculates a
time-lapse change in the concentration of the predetermined
substance in the blood flowing through the blood circuit, in
accordance with the clearance calculated by the
clearance-calculating unit.
8. The blood purification apparatus according to claim 7, further
comprising a correcting unit that corrects the clearance calculated
by the clearance-calculating unit, in accordance with the
time-lapse change in the concentration of the predetermined
substance that is calculated by the time-lapse-change-calculating
unit.
9. The blood purification apparatus according to claim 1, wherein
dialysis dose Kt is obtained in accordance with the clearance
calculated by the clearance-calculating unit, the dialysis dose Kt
being an index not standardized by V denoting a total body-fluid
volume used in an index Kt/V representing a standardized dose of
dialysis performed by the blood purifier.
10. The blood purification apparatus according to claim 1, wherein
a tolerable number of times of reuse of the blood purifier is
quantitatively evaluated in accordance with the clearance
calculated by the clearance-calculating unit.
11. The blood purification apparatus according to claim 1, wherein
the blood circuit and the blood purifier are attached.
Description
FIELD
The present invention relates to a blood purification apparatus
capable of calculating clearance as a figure of merit representing
the degree of solute removal by a blood purifier.
BACKGROUND
Hemodialysis treatment is a kind of blood treatment of purifying a
patient's blood while causing the blood to extracorporeally
circulate. In hemodialysis treatment, a dialyzer as a blood
purifier through which dialysate is allowed to flow is used, and a
blood circuit through which the patient's blood is caused to
extracorporeally circulate is connected to the dialyzer. The blood
and the dialysate are brought into contact with each other through
semipermeable membranes provided in the dialyzer, whereby waste
matter in the blood or excessive water is removed (the removal of
excessive water is referred to as "ultrafiltration"). The blood
purified by the dialyzer is returned to the patient's body through
a puncture needle. Meanwhile, the waste matter or the excessive
water is drained to the outside together with the dialysate through
a dialysate drain line.
Appropriately evaluating and grasping the performance of the
dialyzer is important in selecting a dialyzer suitable for each of
individual patients. One of indices that represent the performance
of the dialyzer is clearance (CL), which is a figure of merit
representing the degree of solute removal by the dialyzer.
Clearance (CL) is an index of the volume of urea (the volume of a
predetermined substance) removed from the blood having flowed into
the dialyzer, and is represented by the unit of blood flow rate
(mL/min). Clearance is obtained by, for example, collecting the
patient's blood and testing the collected blood with an external
measurement device.
Such a method requires blood collection before blood measurement or
the like to be performed with an external measurement device.
Therefore, for example, blood purification apparatuses have been
proposed by PTL 1 and PTL 2, in each of which an increase in
Na.sup.+ in waste dialysate, resulting from the purification, at an
increase in the concentration of Na.sup.+ in the dialysate on the
supply side is regarded as a change in conductivity, whereby the
clearance (Na.sup.+ clearance) is measured. Hence, the clearance
can be obtained without blood collection.
Examples may be found in PTL 1: U.S. Pat. No. 6,702,774 and PTL 2:
U.S. Pat. No. 7,815,809, which are expressly incorporated by
reference herein for all purposes.
SUMMARY
However, the above known blood purification apparatuses have a
problem in that clearance cannot be obtained in real time
(continuously) because Na+ needs to be supplied to the patient
periodically.
The present invention has been conceived in view of the above
circumstances and provides a blood purification apparatus capable
of obtaining clearance in real time.
According to the teachings herein, there is provided a blood
purification apparatus to which a blood circuit that allows a
patient's blood to extracorporeally circulate and a blood purifier
connected to the blood circuit and that purifies the blood in
extracorporeal circulation are attachable, the blood purification
apparatus including a dialysate introduction line through which
dialysate is introduced into the blood purifier; a dialysate drain
line through which waste dialysate resulting from blood
purification performed by the blood purifier is drained from the
blood purifier; and a concentration-detecting unit that detects a
concentration of a predetermined substance in the waste dialysate
resulting from the blood purification by the blood purifier and
flowing through the dialysate drain line. The blood purification
apparatus includes a control unit that establishes a state of
equilibrium where the concentration of the predetermined substance
in the waste dialysate flowing through the dialysate drain line and
a concentration of the predetermined substance in the blood flowing
through the blood circuit are equal or approximate to each other; a
storage unit storing a value detected by the
concentration-detecting unit in the state of equilibrium as an
equilibrium value; and a clearance-calculating unit that calculates
clearance in accordance with the value detected by the
concentration-detecting unit and the equilibrium value stored in
the storage unit, the clearance being a figure of merit
representing a degree of solute removal by the blood purifier.
According to the teachings herein, in the blood purification
apparatus taught herein, the clearance-calculating unit calculates
clearance through a mathematical expression CL=(Cd/Cdeq).times.Qd
(where CL denotes clearance, Cd denotes the concentration of the
predetermined substance detected by the concentration-detecting
unit, Cdeq denotes the equilibrium value stored in the storage
unit, and Qd denotes dialysate flow rate).
According to the teachings herein, in the blood purification
apparatus taught herein, the control unit establishes the state of
equilibrium by reducing or stopping the dialysate flow rate,
increasing the blood flow rate, or causing the dialysate to
circulate through the blood purifier.
According to the teachings herein, in the blood purification
apparatus taught herein, the concentration-detecting unit includes
a light-emitting portion that emits light toward the waste
dialysate, a light-receiving portion that receives the light
emitted from the light-emitting portion and transmitted through the
waste dialysate, and a detecting portion that detects absorbance in
accordance with an intensity of the light received by the
light-receiving portion, the concentration-detecting unit detecting
the concentration of the predetermined substance in the waste
dialysate in accordance with the absorbance detected by the
detecting portion.
According to the teachings herein, in the blood purification
apparatus taught herein, the storage unit stores, as the
equilibrium value, the absorbance detected by the detecting portion
in the state of equilibrium, and the clearance-calculating unit
calculates clearance in accordance with the absorbance detected by
the detecting portion and the equilibrium value stored in the
storage unit.
According to the teachings herein, in the blood purification
apparatus taught herein, the clearance-calculating unit calculates
clearance through a mathematical expression CL=(Abs/Abseq).times.Qd
(where CL denotes clearance, Abs denotes the absorbance detected by
the detecting portion, Abseq denotes the equilibrium value stored
in the storage unit, and Qd denotes dialysate flow rate).
According to the teachings herein, the blood purification apparatus
taught herein includes a time-lapse-change-calculating unit that
calculates a time-lapse change in the concentration of the
predetermined substance in the blood flowing through the blood
circuit, in accordance with the clearance calculated by the
clearance-calculating unit.
According to the teachings herein, the blood purification apparatus
taught herein further includes a correcting unit that corrects the
clearance calculated by the clearance-calculating unit, in
accordance with the time-lapse change in the concentration of the
predetermined substance that is calculated by the
time-lapse-change-calculating unit.
According to the teachings herein, in the blood purification
apparatus taught herein, dialysis dose Kt is obtained in accordance
with the clearance calculated by the clearance-calculating unit,
the dialysis dose Kt being an index not standardized by V denoting
a total body-fluid volume used in an index Kt/V representing a
standardized dose of dialysis performed by the blood purifier.
According to the teachings herein, in the blood purification
apparatus taught herein, a tolerable number of times of reuse of
the blood purifier is quantitatively evaluated in accordance with
the clearance calculated by the clearance-calculating unit.
According to the teachings herein, the blood circuit and the blood
purifier are attached to the blood purification apparatus taught
herein.
According to the teachings herein, a state of equilibrium is
established where the concentration of the predetermined substance
in the waste dialysate flowing through the dialysate drain line and
the concentration of the predetermined substance in the blood
flowing through the blood circuit are equal or approximate to each
other. Furthermore, the value detected by the
concentration-detecting unit in the state of equilibrium is stored
as an equilibrium value. Furthermore, clearance as a figure of
merit representing the degree of solute removal by the blood
purifier is calculated in accordance with the value detected by the
concentration-detecting unit and the equilibrium value stored in
the storage unit. Therefore, clearance can be obtained in real
time.
According to the teachings herein, the clearance-calculating unit
calculates clearance through the mathematical expression
CL=(Cd/Cdeq).times.Qd (where CL denotes clearance, Cd denotes the
concentration of the predetermined substance detected by the
concentration-detecting unit, Cdeq denotes the equilibrium value
stored in the storage unit, and Qd denotes dialysate flow rate).
Therefore, clearance can be calculated correctly and easily with
the concentration-detecting unit, which detects the concentration
of the predetermined substance in the waste dialysate.
According to the teachings herein, the control unit establishes the
state of equilibrium by reducing or stopping the dialysate flow
rate, increasing the blood flow rate, or causing the dialysate to
circulate through the blood purifier. Thus, a state of equilibrium
can be established simply and easily.
According to the teachings herein, the concentration-detecting unit
includes the light-emitting portion that emits light toward the
waste dialysate, the light-receiving portion that receives the
light emitted from the light-emitting portion and transmitted
through the waste dialysate, and the detecting portion that detects
absorbance in accordance with the intensity of the light received
by the light-receiving portion, the concentration-detecting unit
detecting the concentration of the predetermined substance in the
waste dialysate in accordance with the absorbance detected by the
detecting portion. Therefore, the concentration of the
predetermined substance in the waste dialysate can be detected
accurately without bringing the waste dialysate into contact with
any sensor or the like.
According to the teachings herein, the storage unit stores the
absorbance detected by the detecting portion in the state of
equilibrium as an equilibrium value, and the clearance-calculating
unit calculates clearance in accordance with the absorbance
detected by the detecting portion and the equilibrium value stored
in the storage unit. Therefore, clearance can be obtained in real
time by utilizing the ratio of the absorbance that correlates with
the ratio of the concentration of the predetermined substance.
According to the teachings herein, the clearance-calculating unit
calculates clearance through the mathematical expression
CL=(Abs/Abseq).times.Qd (where CL denotes clearance, Abs denotes
the absorbance detected by the detecting portion, Abseq denotes the
equilibrium value stored in the storage unit, and Qd denotes
dialysate flow rate). Therefore, clearance can be calculated
correctly and easily by utilizing the ratio of the absorbance that
correlates with the ratio of the concentration of the predetermined
substance.
According to the teachings herein, the blood purification apparatus
includes the time-lapse-change-calculating unit that calculates the
time-lapse change in the concentration of the predetermined
substance in the blood flowing through the blood circuit, in
accordance with the clearance calculated by the
clearance-calculating unit. Therefore, the concentration of the
predetermined substance in the blood flowing through the blood
circuit at the current time or at any point of time thereafter can
be estimated.
According to the teachings herein, the blood purification apparatus
includes the correcting unit that corrects the clearance calculated
by the clearance-calculating unit, in accordance with the
time-lapse change in the concentration of the predetermined
substance that is calculated by the time-lapse-change-calculating
unit. Therefore, even if the concentration of the predetermined
substance in the blood flowing through the blood circuit changes
with the progress of the blood purification treatment, the
clearance can be corrected correspondingly, with an estimation of
the concentration to be observed after such a change.
According to the teachings herein, dialysis dose Kt as an index not
standardized by V denoting the total body-fluid volume used in the
index Kt/V representing the standardized dose of dialysis performed
by the blood purifier is calculated in accordance with the
clearance calculated by the clearance-calculating unit. Therefore,
medical workers including doctors can grasp the index Kt, which is
not standardized by V, in correspondence with their intention.
According to the teachings herein, the tolerable number of times of
reuse of the blood purifier is quantitatively evaluated in
accordance with the clearance calculated by the
clearance-calculating unit. Therefore, if the treatment is
repeatedly given to one specific patient with one specific blood
purifier, the tolerable number of times of reuse of that specific
blood purifier can be evaluated objectively and appropriately.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a blood purification apparatus according to
an embodiment of the present invention.
FIG. 2 is a diagram of a concentration-detecting unit included in
the blood purification apparatus.
FIG. 3 is a flow chart illustrating a control process undergone by
the blood purification apparatus.
FIG. 4 includes a graph illustrating, with an equilibrium value
(Cdeq or Abseq), a relationship between dialysate flow rate (Qd)
and a detected value (Cd or Abs) observed in a process of
establishing a state of equilibrium by the blood purification
apparatus (a process of reducing the dialysate flow rate), and a
graph illustrating a corresponding relationship between dialysate
flow rate (Qd) and clearance (CL).
FIG. 5 includes a graph illustrating, with an equilibrium value
(Cbeq or Abseq), a relationship between blood flow rate (Qb) and a
detected value (Cb or Abs) observed in a process of establishing a
state of equilibrium by the blood purification apparatus (a process
of increasing the blood flow rate), and a graph illustrating a
corresponding relationship between blood flow rate (Qb) and
clearance (CL).
FIG. 6 is a graph illustrating the value (Abs) detected by the
concentration-detecting unit (a solid line) and the equilibrium
value (Abseq) (a broken line) that change with time.
DETAILED DESCRIPTION
Embodiments of the present invention will now be described
specifically with reference to the drawings.
A blood purification apparatus according to an embodiment is
provided for purifying a patient's blood while causing the blood to
extracorporeally circulate, and is applied to a hemodialysis
apparatus intended for hemodialysis treatment. As illustrated in
FIG. 1, the hemodialysis apparatus basically includes a blood
circuit 1 for causing the patient's blood to extracorporeally
circulate, a dialyzer 2 as a blood purifier, a
waste-liquid-concentration sensor 5 as a concentration-detecting
unit, and a dialysis device 6 capable of performing ultrafiltration
while supplying dialysate to the dialyzer 2. The dialysis device 6
includes a dialysate introduction line 7 and a dialysate drain line
8, a control unit 11, a storage unit 12, a clearance-calculating
unit 13, a time-lapse-change-calculating unit 15, and a correcting
unit 16.
As illustrated in the drawing, the blood circuit 1 basically
includes an arterial blood circuit 1a and a venous blood circuit 1b
each formed of a flexible tube. The dialyzer 2 is connected between
the arterial blood circuit 1a and to the venous blood circuit 1b.
The arterial blood circuit 1a is provided with an arterial
(blood-removal or blood-collection) puncture needle a at a distal
end thereof and with a peristaltic blood pump 3 and an air-trap
chamber 4a for bubble removal at respective halfway positions
thereof. The venous blood circuit 1b is provided with a venous
(blood-return) puncture needle b at a distal end thereof and with
an air-trap chamber 4b for bubble removal at a halfway position
thereof.
When the blood pump 3 is activated with the arterial puncture
needle (a) and the venous puncture needle (b) being punctured in
the patient, the patient's blood flows through the arterial blood
circuit 1a while undergoing bubble removal in the air-trap chamber
4a, and reaches the dialyzer 2, where the blood is purified and
ultrafiltered. Then, the blood flows through the venous blood
circuit 1b while undergoing bubble removal in the air-trap chamber
4b, and returns into the patient's body. Thus, the patient's blood
is purified by the dialyzer 2 while being caused to
extracorporeally circulate through the blood circuit 1. In this
specification, the side of the puncture needle provided for blood
removal (blood collection) is referred to as the "arterial" side,
and the side of the puncture needle provided for blood return is
referred to as the "venous" side. The "arterial" side and the
"venous" side are not defined in accordance with which of the
artery and the vein is to be the object of puncture.
The dialyzer 2 (the blood purifier) has, in a housing thereof, a
blood introduction port 2a, a blood delivery port 2b, a dialysate
introduction port 2c, and a dialysate delivery port 2d. The blood
introduction port 2a is connected to a proximal end of the arterial
blood circuit 1a. The blood delivery port 2b is connected to a
proximal end of the venous blood circuit 1b. The dialysate
introduction port 2c and the dialysate delivery port 2d are
connected to distal ends of the dialysate introduction line 7 and
the dialysate drain line 8, respectively, extending from the
dialysis device 6.
The dialyzer 2 houses a plurality of hollow fibers. The inside of
each of the hollow fibers serves as a blood flow route. The space
between the outer peripheral surface of each of the hollow fibers
and the inner peripheral surface of the housing serves as a
dialysate flow route. The hollow fibers each have a number of very
small holes (pores) extending therethrough from the outer
peripheral surface to the inner peripheral surface, thereby forming
a hollow fiber membrane. Waste matter, excessive water, and the
like contained in the blood are allowed to penetrate through the
membranes into the dialysate.
The dialysis device 6 includes a duplex pump (P), a bypass line 9
connected to the dialysate drain line 8 in such a manner as to
bypass a drain-side pump chamber of the duplex pump (P), and an
ultrafiltration pump 10 connected to the bypass line 9. The duplex
pump (P) is provided over the dialysate introduction line 7 and the
dialysate drain line 8. The duplex pump (P) is provided for
introducing the dialysate into the dialyzer 2 through the dialysate
introduction line 7 and draining the dialysate in the dialyzer 2,
together with the waste matter in the blood, through the dialysate
drain line 8. The duplex pump (P) may be replaced with another
device (such as a device employing a so-called balancing chamber or
the like).
One end of the dialysate introduction line 7 is connected to the
dialyzer 2 (the dialysate introduction port 2c), and the other end
is connected to a dialysate supply device (not illustrated) that
prepares a dialysate at a predetermined concentration. One end of
the dialysate drain line 8 is connected to the dialyzer 2 (the
dialysate delivery port 2d), and the other end is connected to a
drainage unit (not illustrated). Hence, the dialysate introduction
line 7 allows the dialysate supplied from the dialysate supply
device to be introduced into the dialyzer 2, while the dialysate
drain line 8 allows waste dialysate resulting from the blood
purification performed by the dialyzer 2 to be drained from the
dialyzer 2 to the drainage unit.
The ultrafiltration pump 10 is provided for removing water
(excessive water) from the patient's blood flowing through the
dialyzer 2. Specifically, when the ultrafiltration pump 10 is
activated, the volume of liquid drained through the dialysate drain
line 8 exceeds the volume of dialysate introduced through the
dialysate introduction line 7. Hence, water is removed from the
blood by a volume corresponding to the excess.
The waste-liquid-concentration sensor 5 (the
concentration-detecting unit) is provided on the dialysate drain
line 8 in the dialysis device 6 and detects the concentration of a
predetermined substance (for example, the concentration of a
substance such as urea or uric acid contained in the waste
dialysate) contained in the liquid (in the present embodiment, the
waste dialysate drained from the dialyzer 2 as the blood purifier)
that flows with the blood purification performed by the dialyzer 2.
As illustrated in FIG. 2, the waste-liquid-concentration sensor 5
basically includes a light-emitting portion 17, a light-receiving
portion 18, and a detecting portion 19. The light-emitting portion
17 and the light-receiving portion 18 are positioned across the
dialysate drain line 8 from each other.
The light-emitting portion 17 is a light source such as an LED and
emits light (ultraviolet light (UV)) to the liquid (in the present
embodiment, the waste dialysate drained from the dialyzer 2). The
light transmitted through the liquid is receivable by the
light-receiving portion 18. The light-receiving portion 18
according to the present embodiment is a light-receiving device
capable of generating a voltage corresponding to the intensity of
the light received. The detecting portion 19 detects the
concentration of the waste dialysate in accordance with the voltage
corresponding to the intensity of the received light. The detecting
portion 19 detects the absorbance in accordance with the intensity
of the light received by the light-receiving portion 18, and thus
detects the concentration of the predetermined substance in the
waste dialysate (the concentration of urea or the like) in
accordance with the absorbance.
Specifically, when light is emitted from the light-emitting portion
17 while the waste dialysate is flowing through the dialysate drain
line 8, the light is transmitted through the waste dialysate
flowing through the dialysate drain line 8. The light is absorbed
by an amount corresponding to the concentration of the waste
dialysate, and is eventually received by the light-receiving
portion 18. Then, a signal representing the intensity of the light
received by the light-receiving portion 18 (i.e., the voltage
generated in correspondence with the intensity of the received
light) is transmitted to the detecting portion 19, where the
absorbance is calculated in accordance with the light intensity
measured. Thus, the concentration of the waste dialysate flowing
through the dialysate drain line 8 is obtained.
The waste-liquid-concentration sensor 5 according to the present
embodiment is an optical sensor including the light-emitting
portion 17 that emits ultraviolet light (UV) at a wavelength of
about 300 nm (280 to 320 nm). Alternatively, the
waste-liquid-concentration sensor 5 may be an optical sensor that
emits another kind of light such as infrared light, or an enzyme
sensor or the like instead of an optical sensor. While the
waste-liquid-concentration sensor 5 according to the present
embodiment is provided at a position of the dialysate drain line 8
on the upstream side with respect to the duplex pump P (on the side
connected to the dialyzer 2), the waste-liquid-concentration sensor
5 may be provided on the downstream side with respect to the duplex
pump (P).
The control unit 11 is a microcomputer or the like provided in the
dialysis device 6 and establishes a state of equilibrium where the
concentration of the predetermined substance (the concentration of
the waste matter such as urea) in the waste dialysate flowing
through the dialysate drain line 8 and the concentration of the
predetermined substance (the concentration of the waste matter such
as urea) in the blood flowing through the blood circuit 1 (at the
inlet of the dialyzer 2) are equal or approximate to each other.
Specifically, as illustrated in FIG. 4, while the dialysate flow
rate (Qd) is reduced gradually, the concentration (Cd) or the
absorbance (Abs) is detected at each of points A to D by the
waste-liquid-concentration sensor 5, whereby a graph representing a
relationship between the dialysate flow rate (Qd) and the
concentration (Cd) or the absorbance (Abs) can be obtained. The
state where the concentration of the predetermined substance in the
waste dialysate flowing through the dialysate drain line 8 and the
concentration of the predetermined substance in the blood flowing
through the blood circuit 1 are approximate to each other indicates
that the ratio between the two concentrations falls within a range
of 0.7 to 1.3. The ratio between the two concentrations is
preferably within a range of 0.8 to 1.2, more preferably within a
range of 0.9 to 1.1.
In such a state, even if the dialysate flow rate (Qd) is reduced
from the point D, the concentration (Cd) or the absorbance (Abs)
remains constant (such a constant value is referred to as
equilibrium value (equilibrium concentration Cdeq or equilibrium
absorbance Abseq)). Therefore, it is understood that a "state of
equilibrium" has been established where the concentration of the
predetermined substance (the concentration of the waste matter such
as urea) in the waste dialysate flowing through the dialysate drain
line 8 and the concentration of the predetermined substance (the
concentration of the waste matter such as urea) in the blood
flowing through the blood circuit 1 are equal or approximate to
each other.
The storage unit 12 is electrically connected to the control unit
11 and to the waste-liquid-concentration sensor 5 and is capable of
storing, as an "equilibrium value", the value detected by the
waste-liquid-concentration sensor 5 (the concentration-detecting
unit) in the state of equilibrium (i.e., the concentration (Cdeq)
of the predetermined substance or the absorbance (Abseq) observed
in the state of equilibrium). That is, the control unit 11
establishes a state of equilibrium, and the value detected by the
waste-liquid-concentration sensor 5 in the state of equilibrium is
stored in the storage unit 12 as an equilibrium value (an
equilibrium concentration (Cdeq) or an equilibrium absorbance
(Abseq)).
The clearance-calculating unit 13 is capable of calculating
"clearance (CL)" in accordance with the value detected by the
waste-liquid-concentration sensor 5 and the equilibrium value (the
equilibrium concentration (Cdeq) or the equilibrium absorbance
(Abseq)) stored in the storage unit 12. Clearance (CL) is a figure
of merit representing the degree of solute removal by the dialyzer
2. The clearance-calculating unit 13 according to the present
embodiment obtains clearance (CL) as follows.
Clearance (CL) is a function defined by blood flow rate (Qb),
dialysate flow rate (Qd), and overall mass transfer coefficient
(KoA) alone. It is known that when the dialysate flow rate (Qd) is
small enough with respect to the blood flow rate (Qb) and the
overall mass transfer coefficient (K.sub.0A), the dialysate flow
rate (Qd) serves as the rate-determining factor, which establishes
CL=Qd, regardless of the blood flow rate (Qb) and the overall mass
transfer coefficient (K.sub.0A) (see the following, for example:
Akihiro Yamashita, "Basics of Blood Purification: The Japanese
Journal of Clinical Dialysis", 1999, Vol. 15, No. 8, pp. 101-105,
the teachings of which are expressly incorporated by reference
herein).
Assuming that the amount of adsorption to the purification
membranes in the dialyzer 2 is 0, blood-concentration-based
clearance (CLb) based on blood concentration and
waste-liquid-concentration-based clearance (CLd) based on
waste-dialysate concentration are the same (indicate the same
context). In such a case, clearance CL (CLb and CLd) can be
obtained as the product of the ratio between the concentration (Cd)
of the predetermined substance (urea) in the waste dialysate and
the concentration (Cbi) of the predetermined substance (urea) at
the inlet of the dialyzer 2 in the blood circuit 1, and the
dialysate flow rate (Qd) (i.e., CL=(Cd/Cbi).times.Qd Expression
(a)) (see the following, for example: Michio Mineshima,
"Performance and Evaluation of Dialyzer", "Clinical Engineering",
2011, Vol. 22, No. 5, pp. 407-411, the teachings of which are
expressly incorporated by reference herein).
When dialysate flow rate (Qd) is the rate-determining factor,
clearance (CL) is equal to dialysate flow rate (Qd), as described
above. Hence, Expression (b) given below can be obtained through
Expression (a), and Expression (c) given below can be obtained
through Expression (b). Note that "Cdeq" denotes the concentration
of the predetermined substance (urea) in the waste dialysate when
the dialysate flow rate (Qd) is reduced enough to be the
rate-determining factor. CL/Qd=Cdeq/Cbi=1 Expression (b) Cbi=Cdeq
Expression (c)
That is, when the dialysate flow rate (Qd) is reduced enough to be
the rate-determining factor, the concentration (Cdeq) of the
predetermined substance (urea) in the waste dialysate becomes equal
or approximate to the concentration (Cbi) of the predetermined
substance (urea) at the inlet of the dialyzer 2 in the blood
circuit 1 (Cdeq=Cbi), which corresponds to the "state of
equilibrium" according to the present invention. Hence,
substituting Expression (c) into Expression (a) yields Expression
(d) below. CL=(Cd/Cdeq).times.Qd Expression (d)
The clearance-calculating unit 13 according to the present
embodiment calculates clearance through a mathematical expression
(Expression (d) above) CL=(Cd/Cdeq).times.Qd (where CL denotes
clearance, Cd denotes the concentration of the predetermined
substance detected by the concentration-detecting unit, Cdeq
denotes the equilibrium value stored in the storage unit, and Qd
denotes dialysate flow rate).
Furthermore, it is known that there is a correlation between the
ratio (Cd/Cdeq) of the concentration (Cd) of the predetermined
substance and the ratio (Abs/Abseq) of the absorbance (Abs) at the
waste-liquid-concentration sensor 5 (the concentration-detecting
unit) (see the following, for example: F. Uhlin, I. Fridolin, L. G.
Lindberg et al., "Estimation of Delivered Dialysis Dose by On-Line
Monitoring of the Ultraviolet Absorbance in the Spent Dialysate",
American Journal of Kidney Diseases, 2003, Volume 41, Issue 5, pp.
1026-1036).
Therefore, clearance (CL) can be obtained through Expression (e)
given below, by replacing the ratio (Cd/Cdeq) of the concentration
(Cd) of the predetermined substance in Expression (d) above with
the ratio (Abs/Abseq) of the absorbance (Abs).
CL=(Abs/Abseq).times.Qd Expression (e)
In such a case, the storage unit 12 can store the absorbance
detected by the detecting portion 19 (the concentration-detecting
unit) in the state of equilibrium as an equilibrium value (an
equilibrium absorbance Abseq), and the clearance-calculating unit
13 can calculate clearance in accordance with the absorbance (Abs)
detected by the detecting portion 19 and the equilibrium value
(Abseq) stored in the storage unit 12.
The clearance-calculating unit 13 in the above case calculates
clearance through a mathematical expression (Expression (e) above)
CL=(Abs/Abseq).times.Qd (where CL denotes clearance, Abs denotes
the absorbance detected by the detecting portion, Abseq denotes the
equilibrium value stored in the storage unit, and Qd denotes
dialysate flow rate).
A display unit 14 is capable of displaying the clearance (CL)
calculated by the clearance-calculating unit 13 and is, for
example, a display screen of the dialysis device 6, or a monitor or
the like connected to the dialysis device 6. Since the clearance
(CL) calculated by the clearance-calculating unit 13 is displayed
by the display unit 14, medical workers including doctors can grasp
the clearance accurately. Therefore, the blood purification
treatment (dialysis treatment) can be performed smoothly.
When the blood purification treatment progresses and the
concentration (Cb) of the predetermined substance in the blood
flowing through the blood circuit 1 changes (i.e., when the
concentration is reduced with time), the absorbance (Abs) as the
value detected by the detecting portion 19 of the
waste-liquid-concentration sensor 5 changes (decreases) as
illustrated by the solid line in FIG. 6 from Abt0 (at time t=t0) to
Abt1 (at time t=t1), Abt2 (at time t=t2), and Abt3 (at time t=t3).
Meanwhile, the equilibrium value (the equilibrium absorbance Abs)
also changes (decreases) as illustrated by the broken line in the
drawing from Abst0 to Abst1, Abst2, and Abst3. Such changes also
apply to the concentration (Cd) of the predetermined substance
detected by the waste-liquid-concentration sensor 5.
Therefore, the establishment of a state of equilibrium by the
control unit 11 and the storing of an equilibrium value (an
equilibrium concentration Cdeq or an equilibrium absorbance Abseq)
by the storage unit 12 are performed at predetermined intervals
(for example, at each of times t1, t2, t3, and t4) during the blood
purification treatment, and clearance (CL) is calculated by the
clearance-calculating unit 13 and is changed each time. Thus, the
accuracy of the calculated clearance can be increased.
The time-lapse-change-calculating unit 15 calculates a time-lapse
change (Cb(t)/Cb(0)) in the concentration (Cb) of the predetermined
substance in the blood flowing through the blood circuit 1, in
accordance with the clearance (CL) calculated by the
clearance-calculating unit 13. Specifically, assuming a case of a
solute to which a single-compartment model is applicable, it is
known that the time-lapse change in (Cb) is calculable from (CL)
and total body-fluid volume (V), as can be seen from Expression (f)
given below (see the following, for example: Michio Mineshima,
"Basics of Performance Evaluation of Blood Purifier", Nihon Medical
Center Ltd. (Tokyo), 2002, pp. 14-17 the teachings of which are
expressly incorporated by reference herein). Note that "t" denotes
an arbitrary dialysis time in the blood purification treatment.
Cb(t)/Cb(0)=exp(-(CL.times.t)/V) Expression (f)
Therefore, the concentration (Cb(t)), which is a value obtained at
time t as the concentration (Cb(0)) of the predetermined substance
in the blood flowing through the blood circuit 1, can be obtained
through Expression (f) above, in which the clearance (CL)
calculated by the clearance-calculating unit 13, the patient's
total body-fluid volume (V), and the time (t) are used as
parameters. Hence, the concentration of the predetermined substance
in the blood flowing through the blood circuit 1 at the current
time or at any point of time thereafter can be estimated.
The correcting unit 16 corrects the clearance (CL) calculated by
the clearance-calculating unit 13, in accordance with the
time-lapse change (Cb(t)/Cb(0)) in the concentration of the
predetermined substance that is calculated by the
time-lapse-change-calculating unit 15. Specifically, the correcting
unit 16 is capable of obtaining a clearance CL(t) corrected in
accordance with Expression (g) below.
CL(t)=(Abs(t)/(Abseq(0).times.(Cb(t)/Cb(0))).times.Qd(t) Expression
(g)
As described above, the clearance (CL) calculated by the
clearance-calculating unit 13 is corrected in accordance with the
time-lapse change in the concentration of the predetermined
substance (Cb(t)/Cb(0)) calculated by the
time-lapse-change-calculating unit 15. Therefore, even if the
concentration (Cb) of the predetermined substance in the blood
flowing through the blood circuit 1 changes with the progress of
the blood purification treatment, the clearance (CL) can be
corrected correspondingly, with an estimation of the concentration
to be observed after such a change. Hence, even if the
concentration (Cb) of the predetermined substance in the blood
flowing through the blood circuit 1 changes moment by moment with
the progress of the blood purification treatment, clearance (CL)
can be obtained accurately without repeatedly performing the
establishment of a state of equilibrium and the storing of an
equilibrium value.
Furthermore, in the present embodiment, the clearance (CL)
calculated by the clearance-calculating unit 13 can be used for
calculating dialysis dose Kt, which is a dialysis dose not
standardized by V denoting the total body-fluid volume used in an
index Kt/V representing the standardized dose of dialysis performed
by the dialyzer 2. That is, "Kt(te)" not standardized by V (total
body-fluid volume) is calculable by integrating CL(t) obtained over
time, as defined by Expression (h) below. Note that "te" denotes
the end time of the blood purification treatment. [Math. 1]
Kt.sub.(te)=.intg..sub.0.sup.teCL(t)dt Expression (h)
As described above, Kt (i.e., Kt(te) in Expression (h) above) not
standardized by V denoting the total body-fluid volume used in the
index Kt/V representing the standardized dose of dialysis performed
by the dialyzer 2 is calculated in accordance with the clearance
(CL) calculated by the clearance-calculating unit 13. Therefore,
for example, if the index Kt (Kt(te)) not standardized by V is
displayed by the display unit 14 in correspondence with the
intention of medical workers including doctors, the medical workers
can grasp the index Kt (Kt(te)).
In addition, in the present embodiment, the number of times of
reuse of the dialyzer 2 is quantitatively evaluatable in accordance
with the clearance (CL) calculated by the clearance-calculating
unit 13. Specifically, if the treatment is repeatedly given to one
specific patient with one specific dialyzer 2, for example,
clearance (CL) is calculated by the clearance-calculating unit 13
at the beginning or the end of the treatment and is displayed on
the display unit 14 or stored in the storage unit 12. Hence, the
tolerable number of times of reuse of that specific dialyzer 2 can
be evaluated objectively and appropriately.
Now, a process of calculating clearance that is undergone by the
blood purification apparatus according to the present embodiment
will be described with reference to the flow chart illustrated in
FIG. 3.
First, the blood pump 3 and the duplex pump P are activated with
the arterial puncture needle (a) and the venous puncture needle (b)
being punctured in the patient, whereby blood is caused to flow
into the blood circuit 1 through the dialyzer 2 while dialysate is
caused to flow through the dialysate introduction line 7 and the
dialysate drain line 8. In the above state, in step S1, the
dialysate flow rate (Qd) is reduced by a predetermined value. Then,
in step S2, the process is stopped until the value (the
concentration Cd of the predetermined substance or the absorbance
(Abs)) detected by the waste-liquid-concentration sensor 5 (the
concentration-detecting unit) is stabilized. When the value is
judged to be stabilized, the process proceeds to step S3, where the
relationship between the dialysate flow rate (Qd) and the detected
value (the concentration Cd of the predetermined substance or the
absorbance (Abs)) is stored in the storage unit 12.
Then, in step S4, whether there is any change greater than or equal
to a predetermined threshold in the value detected by the
waste-liquid-concentration sensor 5 (the concentration-detecting
unit) is checked. If there is a change greater than or equal to the
predetermined threshold, the process returns to step S1, where the
dialysate flow rate (Qd) is reduced by a predetermined value.
Furthermore, steps S2 to S4 are performed sequentially. If it is
judged in step S4 that there is no change greater than or equal to
the predetermined threshold in the value detected by the
waste-liquid-concentration sensor 5 (the concentration-detecting
unit) (i.e., if the detected value is judged to be constant), the
process proceeds to step S5, where the detected value is stored as
an equilibrium value (an equilibrium concentration (Cdeq) or an
equilibrium absorbance (Abseq)) in the storage unit 12.
Specifically, as illustrated in FIG. 4, when the dialysate flow
rate (Qd) is sequentially reduced from point (A) to point (D) and
is further reduced from point (D), the value (the concentration
(Cd) of the predetermined substance or the absorbance (Abs))
detected by the waste-liquid-concentration sensor 5 (the
concentration-detecting unit) becomes constant, establishing a
"state of equilibrium". Therefore, the value detected in the state
of equilibrium (at point D) is stored as an equilibrium value (an
equilibrium concentration (Cdeq) or an equilibrium absorbance
(Abseq).
Then, the process proceeds to step S6, where the
clearance-calculating unit 13 calculates clearance (CL) through a
mathematical expression CL=(Cd/Cdeq).times.Qd (where CL denotes
clearance, Cd denotes the concentration of the predetermined
substance detected by the concentration-detecting unit, Cdeq
denotes the equilibrium value stored in the storage unit, and Qd
denotes dialysate flow rate), or a mathematical expression
CL=(Abs/Abseq).times.Qd (where CL denotes clearance, Abs denotes
the absorbance detected by the detecting portion, Abseq denotes the
equilibrium value stored in the storage unit, and Qd denotes
dialysate flow rate).
When the clearance (CL) is obtained in step S6, as illustrated in
FIG. 4, the storage unit 12 can store not only the equilibrium
value (Cdeq or Abseq) and the relationship between the dialysate
flow rate (Qd) and the value (Cd or Abs) detected by the
waste-liquid-concentration sensor 5 (the concentration-detecting
unit) (see the upper graph in the drawing) but also the
relationship between the dialysate flow rate (Qd) and the clearance
(CL) (see the lower graph in the drawing).
According to the present embodiment, a state of equilibrium is
established by reducing the dialysate flow rate (Qd).
Alternatively, a state of equilibrium may be established by
increasing the blood flow rate (Qb). In the latter case, in step
S1, the blood flow rate (Qb) is increased by a predetermined value.
Subsequently, in step S2, the process is stopped until the value
(the concentration Cd of the predetermined substance or the
absorbance (Abs)) detected by the waste-liquid-concentration sensor
5 (the concentration-detecting unit) is stabilized. Then, when the
value is judged to be stabilized, the process proceeds to step S3,
where the relationship between the blood flow rate (Qb) and the
detected value (the concentration Cd of the predetermined substance
or the absorbance (Abs)) is stored in the storage unit 12.
Specifically, as illustrated in FIG. 5, when the blood flow rate
(Qb) is sequentially increased from point (A) to point (D) and is
further increased from point (D), the value (the concentration (Cd)
of the predetermined substance or the absorbance (Abs)) detected by
the waste-liquid-concentration sensor 5 (the
concentration-detecting unit) becomes constant, establishing a
"state of equilibrium". Therefore, the value detected in the state
of equilibrium (at point (D)) is stored as an equilibrium value (an
equilibrium concentration (Cdeq) or an equilibrium absorbance
(Abseq).
The control unit 11 according to the present embodiment establishes
a "state of equilibrium" by reducing the dialysate flow rate (Qd)
or increasing the blood flow rate (Qb) as described above.
Alternatively, a state of equilibrium may be established by setting
the dialysate flow rate (Qd) to 0 (stop supplying the dialysate) or
causing the dialysate to circulate through the dialyzer 2 (the
blood purifier). As described above, the control unit 11
establishes a state of equilibrium by reducing or stopping the
dialysate flow rate (Qd), increasing the blood flow rate (Qb), or
causing the dialysate to circulate through the dialyzer 2. Thus, a
state of equilibrium can be established simply and easily.
According to the above embodiment, a state of equilibrium is
established where the concentration of the predetermined substance
in the waste dialysate flowing through the dialysate drain line 8
and the concentration of the predetermined substance in the blood
flowing through the blood circuit 1 (at the inlet of the dialyzer
2) are equal or approximate to each other. Furthermore, the value
detected by the waste-liquid-concentration sensor 5 (the
concentration-detecting unit) in the state of equilibrium is stored
as an equilibrium value. Furthermore, clearance (CL) is calculated
in accordance with the value (Cd, Abs) detected by the
waste-liquid-concentration sensor 5 and the equilibrium value
(Cdeq, Abseq) stored in the storage unit 12. Therefore, clearance
can be obtained in real time.
Furthermore, the clearance-calculating unit 13 according to the
present embodiment calculates clearance through a mathematical
expression CL=(Cd/Cdeq).times.Qd (where CL denotes clearance, Cd
denotes the concentration of the predetermined substance detected
by the concentration-detecting unit, Cdeq denotes the equilibrium
value stored in the storage unit, and Qd denotes dialysate flow
rate). Therefore, clearance can be calculated correctly and easily
with the waste-liquid-concentration sensor 5 (the
concentration-detecting unit), which detects the concentration of
the predetermined substance in the waste dialysate.
Furthermore, the waste-liquid-concentration sensor 5 (the
concentration-detecting unit) according to the present embodiment
includes the light-emitting portion 17 that emits light toward the
waste dialysate, the light-receiving portion 18 capable of
receiving the light emitted from the light-emitting portion 17 and
transmitted through the waste dialysate, and the detecting portion
19 that detects the absorbance in accordance with the intensity of
the light received by the light-receiving portion 18. Furthermore,
the waste-liquid-concentration sensor 5 detects the concentration
of the predetermined substance in the waste dialysate in accordance
with the absorbance detected by the detecting portion 19.
Therefore, the concentration of the predetermined substance in the
waste dialysate can be detected accurately without bringing the
waste dialysate into contact with any sensor or the like.
According to the present embodiment, the storage unit 12 is capable
of storing the absorbance detected by the detecting portion 19 in
the state of equilibrium as an equilibrium value (Abseq).
Furthermore, the clearance-calculating unit 13 calculates clearance
in accordance with the absorbance (Abs) detected by the detecting
portion 19 and the equilibrium value (Abseq) stored in the storage
unit 12. Therefore, clearance can be obtained in real time by
utilizing the ratio of the absorbance that correlates with the
ratio of the concentration of the predetermined substance.
In particular, the clearance-calculating unit 13 according to the
present embodiment calculates clearance through a mathematical
expression CL=(Abs/Abseq).times.Qd (where CL denotes clearance, Abs
denotes the absorbance detected by the detecting portion, Abseq
denotes the equilibrium value stored in the storage unit, and Qd
denotes dialysate flow rate). Therefore, clearance can be
calculated correctly and easily by utilizing the ratio of the
absorbance that correlates with the ratio of the concentration of
the predetermined substance.
Furthermore, the blood purification apparatus includes the
time-lapse-change-calculating unit 15 that calculates the
time-lapse change in the concentration of the predetermined
substance in the blood flowing through the blood circuit 1 in
accordance with the clearance calculated by the
clearance-calculating unit 13. Therefore, the concentration of the
predetermined substance in the blood flowing through the blood
circuit at the current time or at any point of time thereafter can
be estimated.
Furthermore, the blood purification apparatus includes the
correcting unit 16 that corrects the clearance calculated by the
clearance-calculating unit 13, in accordance with the time-lapse
change in the concentration of the predetermined substance that is
calculated by the time-lapse-change-calculating unit 15. Therefore,
even if the concentration of the predetermined substance in the
blood flowing through the blood circuit 1 changes with the progress
of the blood purification treatment, the clearance can be corrected
correspondingly, with an estimation of the concentration to be
observed after such a change.
Furthermore, dialysis dose Kt as an index not standardized by V
denoting the total body-fluid volume used in the index Kt/V
representing the standardized dose of dialysis performed by the
dialyzer 2 is calculated in accordance with the clearance
calculated by the clearance-calculating unit 13. Therefore, medical
workers including doctors can grasp the index Kt, which is not
standardized by V, in correspondence with their intention.
Specifically, the standardized dialysis dose (Kt/V) is an index
obtained by substituting the difference in the concentration of
urea nitrogen in the waste dialysate between that at the beginning
of the hemodialysis treatment and that at the current time, the
volume of ultrafiltration during the hemodialysis treatment (blood
purification treatment), and the time in the hemodialysis treatment
into a predetermined mathematical expression:
-In(C(e)/C(s)-0.0080+(4-3.5.times.C(e)/C(s)).times.(V.sub.UF/DW)
(where C(s) denotes the urea-nitrogen concentration (initial value)
at the beginning of the hemodialysis treatment, C(e) denotes the
urea-nitrogen concentration at the end of the dialysis, V.sub.UF
denotes ultrafiltration volume, and DW denotes the patient's dry
weight). Therefore, it has been difficult to obtain only the index
Kt that is not standardized by V. In contrast, according to the
present embodiment, only the index Kt that is not standardized by V
can be obtained through Expression (h) given above, in which
clearance is used as a parameter. Therefore, the index Kt that is
not standardized by V can be obtained easily.
In addition, according to the present embodiment, the tolerable
number of times of reuse of the dialyzer 2 is quantitatively
evaluated in accordance with the clearance calculated by the
clearance-calculating unit 13. Therefore, if the treatment is
repeatedly given to one specific patient with one specific dialyzer
2, the tolerable number of times of reuse of that specific dialyzer
2 can be evaluated objectively and appropriately.
While the present embodiment has been described above, the present
invention is not limited thereto. For example, the value detected
by the waste-liquid-concentration sensor 5 (the
concentration-detecting unit) and the equilibrium value that are to
be used for calculating the clearance may be replaced with other
parameters, as long as such parameters each correlate with the
concentration of the predetermined substance. For example, factors
such as the voltage or the current outputted by the
waste-liquid-concentration sensor 5 may be employed in addition to
the absorbance. Moreover, the mathematical expressions for
calculating clearance by the clearance-calculating unit 13 are not
limited to those given above, and may be other mathematical
expressions.
While the present embodiment concerns a case where the calculated
clearance is displayed on the display unit 14, the calculated
clearance may be informed to medical workers including doctors
through another unit such as a speaker. Alternatively, instead of
providing or displaying such information, the clearance calculated
by the clearance-calculating unit 13 may be, for example,
exclusively used for internal processing performed for making
settings of the treatment. While the present embodiment is applied
to a hemodialysis apparatus, the present invention may also be
applied to a blood purification apparatus intended for another
treatment (such as hemofiltration treatment or hemodiafiltration
treatment) for purifying blood while causing the blood to
extracorporeally circulate.
The present invention is applicable to any blood purification
apparatus, including those having other additional functions, as
long as the apparatus includes a control unit that establishes a
state of equilibrium where the concentration of a predetermined
substance in waste dialysate flowing through a dialysate drain line
and the concentration of the predetermined substance in blood
flowing through a blood circuit are equal or approximate to each
other, a storage unit capable of storing a value detected by a
concentration-detecting unit in the state of equilibrium as an
equilibrium value, and a clearance-calculating unit capable of
calculating clearance in accordance with the value detected by the
concentration-detecting unit and the equilibrium value stored in
the storage unit, the clearance being a figure of merit
representing the degree of solute removal by a blood purifier.
REFERENCE SIGN LIST
1 blood circuit 1a arterial blood circuit 1b venous blood circuit 2
dialyzer (blood purifier) 3 blood pump 4a, 4b air-trap chamber 5
waste-liquid-concentration sensor (concentration-detecting unit) 6
dialysis device 7 dialysate introduction line 8 dialysate drain
line 9 bypass line 10 ultrafiltration pump 11 control unit 12
storage unit 13 clearance-calculating unit 14 display unit 15
time-lapse-change-calculating unit 16 correcting unit 17
light-emitting portion 18 light-receiving portion 19 detecting
portion P duplex pump
* * * * *